In the automotive industry, it has been a known practice to evaluate the health of starting and/or charging circuit components by measuring a voltage drop corresponding to a specific input current between two separate points of the circuit, and comparing the measurement with specification values. For instance, for determining the health of a starting circuit (which may include a starter, a battery, a solenoid, cables and terminals) in an automotive vehicle, a technician is often asked to use a voltmeter to measure a voltage drop between the positive terminal of the starter and the positive terminal of the vehicle's battery while the starter is cranking the engine. This can be a cumbersome task, sometimes requiring an additional technician to monitor the voltage display while the other technician cranks the vehicle at the same time. If the current flowing through to the starter is normal, the measured voltage drop will be within an acceptable range specified by the manufacturer. If an abnormal voltage drop is found, further investigation may be needed to determine the cause of the abnormality. For example, a possible cause to the abnormal voltage drop may be that the resistance or impedance of a cable connecting the starter and battery is too high. In order to isolate the source of the problem, the technician needs to remove the connecting cable from the starting circuit and uses an ohmmeter to measure the resistance of the cable to determine whether the cable resistance indeed contributes to the abnormal voltage drop. If the cable resistance is normal, the technician will then check the integrity of the connections of the cable terminals to the starter and the cable to the battery. Rust and corrosion are common problems with the terminal connections of the cable which add unwanted resistance to this circuit.
For determining the health of a charging circuit (which includes a battery charged by an alternator, and cables and terminals) in an automotive vehicle, a technician often is asked to use a voltmeter to measure a voltage drop between the positive terminal of the alternator and that of the battery charged by the alternator when the charging circuit is in operation, i.e., a current generated by the alternator is flowing through the battery, to determine whether the measured voltage drop falls within an acceptable range specified by specifications. If an abnormal voltage drop is found, further investigation may be needed to determine the cause of the abnormality. For example, a possible cause to the abnormal voltage drop may be that the resistance or impedance of a cable connecting the alternator and battery is too high. In order to isolate the source of the problem, the technician needs to remove the connecting cable from the charging circuit and uses an ohmmeter to measure the resistance of the cable to determine whether the cable resistance indeed contributes to the abnormal voltage drop.
A shortcoming of the conventional approach is that the multiple steps for measuring the voltage drop and work involved to measure the cable resistance add complexity to the testing procedure and it can be time consuming, thus adding additional expense to the repair cost. Furthermore, the conventional approach requires the starting circuit or charging circuit to be in operation, such that a voltage drop can be measured by the voltmeter. However, the circuit under test is not always in working condition or in operation. In that case, no current is flowing through the circuit, and no voltage drop can be detected by the voltmeter. As a result, the test cannot be performed. Moreover, the specification of a vehicle may require comparing voltage drops using different testing parameters, such as varying starter currents under different engine conditions or different charging currents under different loads.
The starter current can vary depending on temperature and the engine's operating condition. However, it is not always possible to generate or duplicate the required testing parameters as required by the specification. Even if it is possible, it is burdensome to perform multiple tests using various test parameters.
Therefore, a need exists for a tester that would reduce the complexity of circuit testing procedures. There is also a need for a tester that could determine the health of circuits even if the circuits are not in operation or working condition. Another need exists to allow a user to predict circuit responses corresponding to different testing parameters, without the need to actually conduct multiple tests using the different testing parameters.